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    <script>
        // let a = 10;
        /*    a > 0 && a < 20 ? (a++ , console.log(a)) : null;
           if (a > 0 && a < 20) {
               a++;
               console.log(a);
           } */

        // let a = 10;
        // a > 0 ? (a < 10 ? a++ : a--) : (a > -10 ? a += 2 : null);

        /*   if (a > 0) {
                if (a < 10) {
                    a++;

                } else {
                    a--;
                }
            } else {
                if (a > -10) {
                    a += 2;
                }
            } */

        /*    let a = 1;
           switch (a) {
               case 1: console.log("哈哈");
               case 5: console.log('嘿嘿5');
                   break;
               case 9: console.log('滴滴9');
                   break;
               case 10: console.log('嘻嘻10');
                   break;
               default: console.log('哦豁');//以上都不成立
           } */





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